The present invention relates generally to vapor deposition onto a structure of an organic layer which will form part of an organic light-emitting device (OLED). More particularly, the present invention relates to a thermal physical vapor deposition apparatus which includes an elongated vapor distributor disposed in a chamber at reduced pressure and spaced from a structure, one or more detachable organic material vapor sources disposed outside of the chamber, and a vapor transport device connecting each vapor source to the vapor distributor.
An organic light-emitting device, also referred to as an organic electroluminescent device, can be constructed by sandwiching two or more organic layers between first and second electrodes.
In a passive matrix organic light-emitting device (OLED) of conventional construction, a plurality of laterally spaced light-transmissive anodes, for example indium-tin-oxide (ITO) anodes, are formed as first electrodes on a light-transmissive substrate such as, for example, a glass substrate. Two or more organic layers are then formed successively by vapor deposition of respective organic materials from respective sources, within a chamber held at reduced pressure, typically less than 10xe2x88x923 torr (1.33xc3x9710xe2x88x921 pascal). A plurality of laterally spaced cathodes is deposited as second electrodes over an uppermost one of the organic layers. The cathodes are oriented at an angle, typically at a right angle, with respect to the anodes.
Applying an electrical potential (also referred to as a drive voltage) operates such conventional passive matrix organic light-emitting devices between appropriate columns (anodes) and, sequentially, each row (cathode). When a cathode is biased negatively with respect to an anode, light is emitted from a pixel defined by an overlap area of the cathode and the anode, and emitted light reaches an observer through the anode and the substrate.
In an active matrix organic light-emitting device (OLED), an array of anodes are provided as first electrodes by thin-film transistors (TFTs) which are connected to a respective light-transmissive portion. Two or more organic layers are formed successively by vapor deposition in a manner substantially equivalent to the construction of the aforementioned passive matrix device. A common cathode is deposited as a second electrode over an uppermost one of the organic layers. The construction and function of an active matrix organic light-emitting device is described in U.S. Pat. No. 5,550,066, the disclosure of which is herein incorporated by reference.
Organic materials, thicknesses of vapor-deposited organic layers, and layer configurations, useful in constructing an organic light-emitting device, are described, for example, in U.S. Pat. Nos. 4,356,429, 4,539,507, 4,720,432, and 4,769,292, the disclosures of which are herein incorporated by reference.
In past and current practice of forming a vapor-deposited organic layer on an OLED substrate or structure, a vapor deposition source is disposed in a chamber which is evacuated to provide a reduced pressure as low as 10xe2x88x926 torr (1.33xc3x9710xe2x88x924 pascal). The OLED substrate or structure is also disposed in the chamber and spaced from the vapor deposition source. The source has received, prior to evacuation of the chamber, solid organic material which can be vaporized. When the source is operative, a portion of the solid organic material is vaporized, generally by sublimation, and vapor of organic material condenses on the OLED substrate or structure to form an organic layer.
A particular problem arises from using a vapor deposition source which is disposed in an evacuated chamber: when the solid organic material in the source has been depleted or used up after multiple substrates or structures have been coated with an organic layer, the chamber has to be vented to atmospheric pressure so that the chamber can be opened for removal and/or replacement of the depleted source, or to recharge the source with solid organic material. Such venting, and subsequent evacuation of the chamber, can be time-consuming because opening the chamber to the ambient atmosphere can result in adsorption of moisture in the chamber and its internal components. It is well known in the art of vacuum system technology that such adsorbed moisture can significantly increase the time required to evacuate a chamber to achieve the reduced pressure in the chamber which had been maintained prior to venting and opening the chamber to the ambient environment.
This problem may be compounded in a multi-chamber apparatus which is evacuated by a common vacuum pump facility to achieve a reduced pressure in each chamber of such apparatus or system.
It is an object of the present invention to overcome the problems associated with using a vapor deposition source charged with a solid organic OLED material in a chamber at reduced pressure.
It is another object of the present invention to use one or more detachable organic material vapor sources in making OLED devices.
This object is achieved in a thermal physical vapor deposition apparatus for vaporizing solid organic materials and applying vaporized organic materials as an organic layer onto structure in a chamber at reduced pressure in forming a part of an organic light-emitting device (OLED), comprising:
a) an elongated vapor distributor disposed in the chamber and spaced from the structure, the vapor distributor defining an elongated cavity having a plurality of vapor efflux apertures formed along an elongated direction of the distributor for delivering vaporized organic materials in the space between the distributor and the structure for depositing an organic layer onto the structure;
b) one or more detachable organic material vapor sources which are disposed outside of the chamber and can be attached, and when operative, to deliver vaporized organic materials into the cavity of the vapor distributor; and
c) a vapor transport device dedicated to each of the one or more organic material vapor sources and sealingly extending into the cavity, the vapor transport device including means for detaching or for sealingly attaching an organic material vapor source.
A feature of the present invention is that one or more organic material vapor sources are disposed outside of a chamber held at a reduced pressure and can be detached from a vapor transport device which extends into a vapor distributor disposed in the chamber while maintaining the reduced pressure in the chamber.
Another feature of the present invention is that a plurality of detachable organic material vapor sources which are disposed outside of a chamber held at a reduced pressure can be charged with solid organic materials selected to provide vapors to a vapor distributor disposed in the chamber via a corresponding plurality of vapor transport devices, so that an organic layer of an OLED can be formed on a structure with the layer having selected features.
Another feature of the present invention is that an organic layer of an OLED of improved uniformity can be formed on a structure by providing motion of the structure with respect to a vapor distributor during vapor deposition of the layer.